Metal safe stabilized stripper for removing cured polymeric layers and negative tone acrylic photoresists

ABSTRACT

A stabilized stripping composition is provided for removing fully cured polymeric organic substances from an inorganic substrate, including polyimide and liquid crystal polymer (LCP). The stripping composition comprises about 3 to about 15 percent of benzyltrimethylammonium hydroxide (BTMAH), about 50 to about 87.5 weight percent of n-methylpyrrolidone as a solvent with ethylene glycol ranging from 15 to about 45 weight percent and a stabilizer. The stripping composition preferable also contains a suitable corrosion inhibitor and a non-ionic surfactant. Also provided is a method for stripping thick negative-tone photoresists, e.g. acrylic, styrenic, maleic anhydride, and similar, from inorganic substrates by contacting the polymeric organic substance with the organic stripping BTMAH composition for a period of time sufficient to dissolve and remove said polymeric substances.

BACKGROUND OF THE INVENTION

[0001] This invention relates to metal safe stripping compositions for use in dissolving, i.e. removing, various polymer layers such as polyimide, liquid crystal polymer (LCP) and thick negative-tone acrylic photoresists. More particularly, the invention describes a blend of chemistries to yield a product which performs at elevated temperatures with limited degradation or loss of the active constituents, providing substantially improved stability and allowing for broad processing conditions with accelerated removal and cleaning.

[0002] During the manufacture of semiconductors and semiconductor microcircuits, various polymers may be used for their insulative and chemical resistance properties. These materials, including polyimide and liquid crystal polymer (LCP), are substantially cured to a full cross-link condition to exhibit dense and glass-like qualities allowing them to be incorporated into, or to comprise, the substrate. Through the action of chemicals in both wet (solution) and dry (plasma) forms, further processing is carried out on the substrate, e.g. silicon, silicon dioxide, aluminum, copper, or the cured polymer, etc., to include etch (removal) and deposition (addition). Upon completion, part or all of the exposed polyimide or LCP may need to be stripped (removed).

[0003] In some cases, the microcircuit is coated with a polymeric organic substance, such as a thick film negative-tone acrylic photoresist to form a resist mask after undergoing a photolithography process. Typically, the acrylic resist is formed over inorganic substrates, however, the resist may also be in contact with cured polymer layers such as polyimide and LCP. Although resists are used where etching or deposition is needed, a thick film resist is commonly used when deposition of thick layers of metal, e.g. copper, is needed. Following the metal deposition and after subsequent rinsing or conditioning, it is necessary that the thick resist mask and any residue be removed to leave behind the thick deposited pattern of metallization.

[0004] A common method used in removing cured polymer or resist mask from the substrate is by direct contact with an organic stripper. The chemistry of the stripper is such that it penetrates the material surface and may undergo a reaction to sever cross-linked portions and facilitate the swelling, dissolution, and lifting from the surface of the underlying substrate. The protected area of the substrate is then revealed. The substrate protected area is typically inorganic, e.g. silicon, its native oxide, a hybrid compound semiconductor, such as gallium arsenide, and may include sensitive metallic microcircuity, such as, aluminum or copper; or the underlying area may be organic, e.g. cured polymer to include polyimide or LCP.

[0005] Where a thick resist must be removed from underlying cured polymer and potentially in contact with metallization, selectivity towards the resist over the polymer and metal must be achieved. In certain cases, the underlying cured polymer must be removed using the same approach, yet with a more aggressive stripper or conditions. Prior stripping compositions have usually been less than satisfactory or have the distinct disadvantage of unacceptable toxicity and/or presenting pollution problems from the disposal of such compounds as phenol, cresol, sulfonic acid, and chlorinated hydrocarbons. Other prior art of stripping compositions for removing polymeric organic substances, for example, comprise aqueous sulfuric acid containing a significant amount of fluoride ion to reduce metallic dulling and corrosion, as exemplified in U.S. Pat. No. 3,932,130. When operated at elevated temperatures, some photoresist strippers require the presence of fluoride ion stabilizers to prevent metallic corrosion, especially towards aluminum and copper.

[0006] There is a need, accordingly, for improved stripping compositions which will remove the thick acrylic resist from cured polymer, and in some cases, to remove the cured polymer. In either application safety towards other underlying and adjacent substances, such as, the substrate and metallic circuitry, in preventing corroding, gouging, dissolving, dulling, or otherwise marring these surfaces is a requirement. Also the efficiency and selectivity of the stripper is extremely desirable.

[0007] It is an object of this invention to provide organic stripping compositions which operate effectively while avoiding the prior mentioned toxic substances and at moderate or high temperatures, to clean effectively and quickly, cured polymer and thick film negative tone photoresist from metallized or inorganic substrates. It is another object of this invention to provide organic stripping compositions which are highly effective for removing thick film negative tone photoresists, particularly those comprising acrylic, styrene, novolak, and related polymers, which in the presence of certain cross-linking photoinitiators, will cure to a hard and highly chemically resistant framework. In the removal process of cured polymer and resist, selectivity must be achieved on the material to be removed over the unwanted etch or damage to the substrate or corrosion and dulling of metallic circuitry present as adjacent structures.

SUMMARY OF THE INVENTION

[0008] In accordance with this invention, a blend of chemistries is provided to remove cured polymer, such as polyimide and liquid crystal polymer (LCP), and fully-cured thick film negative tone acrylic photoresist. Polymers and resists of this kind will undergo a curing profile either through thermal, chemical, or photoinitiation means and form a dense, hard, and highly chemically resistant framework. Polyimide and LCP are used to isolate conductive portions of the circuit and may be used as a flexible substrate alternative to rigid glass fiber circuit boards. Photoresists are used to produce patterns (masks) which become the basis for depositing microcircuits in semiconductor manufacturing.

[0009] In the past, these chemically resistant layers have been difficult or impossible to fully remove, usually resulting in a time consuming and expensive process. The present invention affords a means to remove the resist mask from the circuit and to rework the insulative polymer. Upon exposure to the system of the invention at given conditions, the cured polymer or resist will begin to breakdown and dissolve, allowing the by-products to be rinsed away with water. Removal rates will vary depending upon polymer type, extent of cure, thickness, and processing (removal) conditions. Heat and agitation will generally accelerate removal and may help to achieve selectivity in removing a resist over a polyimide or LCP. Increased heat is required to remove cured polyimide or LCP. The composition of the invention also includes a stabilizer and an inhibitor for metal corrosion.

DETAILED DESCRIPTION OF THE INVENTION

[0010] The present invention provides a novel metal-safe and stabilized formulated chemical composition which quickly and effectively removes cured polymer and thick-film photoresist from a range of substrates, and involves methods of using same.

[0011] The invention employs a high molecular weight and heat stable quaternary ammonium hydroxide (QAH) and, more specifically, benzyl trimethylammonium hydroxide (BTMAH), to maintain a strong alkaline environment to cleave the cross-linked polymer of the kind which is typical of a cured negative tone acrylic photoresist, polyimide, liquid crystal polymer, and other similar materials and allow the solvent of the system invention to penetrate, dissolve, and lift reacted material so that it can be rinsed away. The solvent system is composed of a glycol to assist in stabilizing the BTMAH and a cyclic ketone that is ideal for polymer dissolution. Additives also include a stabilizer to terminate internal reactions between BTMAH and the ketone, a blend of triazole-based corrosion inhibitors to protect free copper and aluminum, and a surfactant used to penetrate small geometries and aid in rinsing. Although the QAH compounds are chosen for alkaline saponifying and emulsification of polymers, the BTMAH offers added heat stability and bath life, enabling the product to be used at elevated temperatures for tenacious polymer coatings. When the BTMAH is combined with the selected solvents and suitable additives, the chemical system becomes an excellent medium for processing microelectronic parts where performance must be maintained for extended periods of time with high loading capacity and where safety and integrity of the substrate and adjacent metal devices must be carefully preserved.

[0012] While the novel composition of the invention is described for use in microelectronic applications to remove cured negative-tone acrylic photoresist, the product has also been proven useful for removal of other cured polymer such as polyimide and liquid crystal polymer (LCP), common surface dielectric (insulator) coatings used in microelectronic manufacturing. The invention also appears to be an excellent choice to remove a variety of other tenacious residue originating from fully cured polymer and photoresist while not affecting the integrity of adjacent materials. Examples include negative-tone acrylic and novolak which have been hard baked (i.e. exposed to high temperatures). The performance and selectivity of the compositions are key characters to specialty products used for high tech applications. Environmentally, the invention is a desirable replacement for toxic or hazardous products (i.e., phenols, sulfuric acid, etc.) used for the same applications.

[0013] The BTMAH stripping compositions of the invention function by maintaining a strong alkaline environment whereby the solvent penetrates and dissolves cross-linked polymer and cured negative-tone acrylic and novolak photoresists. The solvent system is composed of a glycol, e.g., ethylene glycol (EG), to stabilize the BTMAH and cyclic ketone that effects the polymer dissolution. Advantageous additives contained within the stripping composition may include a stabilizer which functions to stop degradative reactions between the BTMAH and the ketone, triazole-based corrosion inhibitors to protect copper and aluminum and a suitable surfactant to aid in penetrating small geometries and in rinsing.

[0014] Like most caustics, QAH compounds are chosen for alkaline saponifying and emulsification of polymers, however, QAH has improved solubility in organic systems over common metal hydroxides. Further, out of the series of QAH compounds available, the BTMAH offers added heat stability and bath life, enabling the product to be used in elevated temperatures for prolonged periods. Heat is commonly used when having to penetrate, dissolve, and lift tenacious polymer coatings. When BTMAH is combined with the selected solvents and additives, the chemical system of the invention affords an excellent vehicle for processing microelectronic parts where reliable performance must be maintained and safety to the substrate and adjacent metal devices is required.

[0015] A typical composition in accordance with the invention comprises the (BTMAH) benzyltrimethylammonium hydroxide, a solvent system and stabilizer, and preferable, includes also, a corrosion inhibitor and a non-ionic surfactant.

[0016] The BTMAH content may vary from about 3 to about 15 weight percent and preferably comprise about 4 to about 8 weight percent of the stripper. BTMAH is an organic solid and is commonly made available in lower alcohols, e.g. methanol, or water. In the invention, the BTMAH is prepared in a stock solution of ethylene glycol (EG). Stock concentrations of BTMAH in EG can run near 50% by weight as BTMAH. To ensure this stock solution of a strong caustic (BTMAH) and EG is stable over time, a stabilizer is added. The preferred stabilizer is paraformaldehyde (PF). The concentration of PF in the final solution (invention mixture) ranges from 300 to 10,000 ppm (1%) and is preferred to be approximately 500 to 1000 ppm.

[0017] The solvent system comprises a cyclic ketone e.g., N-methylpyrrolidone (NMP), Dimethylpiperidone (DMPD), etc. The ketone solvent is employed in amounts from 50 to about 87.5 weight percent and preferably in proportions of about 60 to about 75 weight percent. Other common photoresist solvent families such as amides, aldehydes and certain ketones not mentioned here such as acetone and methylethylketone (MEK) are not stable with BTMAH. Due to the alkaline nature of BTMAH, these solvents tend to react with BTMAH via Hoffman Degradation (amides) and Reductive Amination (aldehydes and certain ketones) to reduce the hydroxide to trimethylamine, neutralize the system, cause a color change i.e. slight yellow to dark brown, which may adversely affect performance. For this reason, certain solvents are avoided to come into contact with BTMAH and therefore are not considered for these compositions.

[0018] In addition to the selected cyclic ketones deemed to be stable with BTMAH, suitable glycol is added to further stabilize the system during processing and to act as a cosolvent. A glycol that may be employed with the BTMAH includes, for example, EG. It has been determined that low molecular weight species appear to be more stable with BTMAH due to their lack of color change. Therefore, even though alternatives to EG exist such as propylene glycol (PG), glycerin, or other polyhydric alcohols, such may not be desirable due to their ability to discolor upon exposure to BTMAH. The actual color intensity observed will depend upon the glycol chosen and the relative concentrations present with respect to BTMAH. Concentrations of the chosen glycol in the invention vary from 15-45% by weight and is preferably between about 20-30% by weight.

[0019] Water may also be added to facilitate selective removal of one polymer over another. This selectivity is needed when two polymers appear to be both soluble in the invention. Addition of water will discriminate one polymer's solubility over another to the extent that selective removal is accomplished. In such removal cases, water makes up approximately 10% by weight of the mix.

[0020] To afford protection for transition metals such as copper and aluminum, a suitable corrosion inhibitor such as BTA (benzyltriazole), TTA (tolytriazole), MBTA (mercaptobenzyltriazole), or combinations thereof, may be incorporated into the stripper composition. Alternatives to these inhibitors include pyrogallol (neutral form of gallic acid) and pyrocatachol (catachol). A preferred corrosion inhibitor for copper and similar soft metal substrates includes a combination of the triazoles, e.g. BTA, TTA, MBTA, and the like, to give a synergistic effect on the desired metal to protect. The combined triazole system comprises a concentration of approximately 0.5 to 5% by weight and is preferably a concentration of from about 1.0 to about 4.0 percent by weight.

[0021] When substantial amounts of transition metal is present as part of the polymer residue and must be complexed during the removal process, a suitable chelating agent such as EDTA (ethylenediaminetetraacetic acid) is preferably also included. The basified and solubilized form of this chelating agent is added to combine these trace metals present in the matrix of the target polymer to be removed. Alternative chelates include the basified versions of DTPA (dietyhylenetriaminepentaacetic acid); NTA (nitrilotriacetic acid), and 2,4-pentanedione. Each of these products is preferably converted to an alkaline form before using in the stripper matrix, otherwise, the “weak acid” tends to react with the product.

[0022] Suitable surfactant includes a non-ionic alkoxylated linear alcohol such as the tradename Polytergent (Pluronic) SL92, available from BASF Corporation. The surfactant functions to reduce surface tension, emulsify dissolved polymer, and aid in water rinsing. The surfactant preferably has a high cloud point (i.e. >60° C.) to allow for heated processing and rinsing. A non-ionic environment is required for non-reaction towards dissolved metals and maximum solubility in non-aqueous chemistries and water. Low foaming capacity allows for product use in various automated equipment. Alternative surfactants include nonyl-phenols and non-ethoxylates with a HLB (hydrophilic/lipophilic balance) ranging from 7-15. Less than about 2 weight percent of the non-ionic surfactant and preferable an amount of about 0.1 to about 1.4 weight percent is sufficient.

[0023] For dissolution and removal of LCP, polyimide, and thick film acrylic resists, the temperature employed for suitable performance is important. Generally, in any polymer removal application, an elevated temperature above about 70° C. is preferred. Although some systems will vary, it is preferred that the dissolution and removal of full-cure LCP and polyimide be conducted at a temperature in the range of about 120° C. to about 130° C. for at least about 20 minutes. Thick film acrylic resists which have been fully-cured and exposed to temperatures of 200° C. are dissolved and removed in most cases within about 5 minutes using a processing temperature of about 80° to 90° C. In all removal applications deionized water is recommended for rinsing.

[0024] The stripping compositions quickly and effectively remove organic polymers from metallized and metallic surfaces without attacking the metal surface, and without using various toxic or intrusive metal corrosion inhibitors. Although the invention has been shown to be safe for aluminum it has been shown to be extremely suitable with copper. When measured on electrodeposited copper on silicon substrates, it was found that the stripping composition removed less than 0.1 Å/min copper at selected temperatures and time.

[0025] The present invention also resides in providing a method of removing a cured thick-film organic polymeric material from an inorganic substrate which comprises contacting the polymeric organic substance with the BTMAH stripping composition for a period of time sufficient to remove the polymeric substances. The solvent system comprises: a) a glycol to stabilize the BTMAH and cyclic ketone for polymer dissolution; b) a stablizer to effectively terminate the internal reaction between the BTMAH and the ketone; c) a corrosion inhibitor, such as triazole based inhibitors to protect metallized areas, such as, free copper and aluminum; and d) a surfactant to penetrate small geometries and act as an aid in rinsing.

[0026] The photoresists which are removed by the stripping solutions of this invention generally comprise acrylic, styrenic, maleic anhydride, and related monomers and copolymers used to produce negative tone photosensitive thick films. These photoresists are processed to apply thick films which can be on the order of >50 microns. They are available in commerce as a dry-film photoresist, e.g. Riston, a product of E.I. duPont deNemours and Co. or Laminar, a product of Shipley Company, L.L.C.. These dry film resists are available as a film of the photosensitive polymer of defined thickness sandwiched between two peel-away plastic coverings, e.g. Mylar® polyester and polyethylene. The resist may also be available as a liquid-base spin-on variety. In this case, the resist is applied by conventional means by delivering a specific volume of the polymer to a substrate and followed by rotating the base to cause the liquid polymer to coat the surface by drawing it from the center to the edge in a uniform manner through centrifugal force resulting from a high rate of spinning.

[0027] Whether the photoresist is a dry film or liquid spin-on variety, it is applied to an inorganic substrate, e.g. aluminum, copper, silicon, silicon dioxide or silicon dioxide metallized with aluminum and where portions thereof are masked. The masked substrate is then exposed to ultra violet (UV) light, e.g. a 120 volt 650 watt quartz lamp for 1-15 seconds at a distance of 1.524-3-3.048×10⁻¹ m, to harden the exposed photoresist. For negative photoresists, the portion of the photoresist which is not exposed, i.e., masked from the light, is then removed by a mild solvent which does not dissolve the exposed photoresist. Thus, a pattern, e.g., a portion of an electrical circuit pattern, is left on the exposed substrate. In preparation of further processing, the remaining photoresist pattern is then baked for further hardening, typically to temperatures approaching 200° C. The portion of the substrate which is not covered by the photoresist is treated by etching (removal) or deposition (addition). In most cases where negative tone resist is used (i.e. a negative slope or close to 90 degree is formed), metal is deposited (added). The hardened photoresist must be removed to leave behind the metal traces and before the substrate can be further processed or used.

[0028] In employing the stripping solutions of this invention, the substrate covered with the baked photoresist is brought into contact with the stripping solution at a temperature of ≧70° C.; additional heating will improve performance and loading capacity. Times required for stripping the photoresist vary to quite an extent depending on the specific polymer used in the photoresist, the photoresist curing prefacing conditions, temperature of the stripper, and agitation of the medium, varying from no agitation (static) to a maximum agitated solution resulting from ultrasonic cavitation action. Generally, the time involved will be less than 10 minutes and during optimized performance conditions, may be measured in seconds, while some photoresist, depending on the baked temperature, may require times of more than 10 minutes and up to 30 to 60 minutes, where lower processing temperatures of the invention stripper are employed on highly polymerized and metallized surfaces. It will be appreciated that many photoresists are completely dissolved from the substrate while others may be loosened, and floated off, and then subsequently dissolved in the stripping composition. Examples of the kind of photoresists which may be stripped by the composition of the present invention are shown in Table I: TABLE I TYPE NEGATIVE TRADEMARKS SOURCE Acrylic THB-Series to include: JSR Micro, Inc. THB-130N, THB-150N Acrylic RISTON Dry Film E.I. duPont deNemours and Co. Acrylic LAMINAR Dry Film Shipley Company, L.L.C. Novolak NFR-Series to include: JSR Micro, Inc. NFR-015, NFR-016D2

[0029] It is to be understood that other negative photoresists having a broad range of molecular weights, as well as the positive-series type, can be effectively removed by the stripping composites of the present invention.

[0030] After the photoresist has been stripped from the substrate, the substrate may then be rinsed in water, or in an alcohol such as isopropanol or other hydrophilic and compatible solvents, e.g. NMP, DMPD, EG, or mixtures thereof; other compatible rinsing solvents well known to one of ordinary skill in the art may also be used.

[0031] While the stripping compositions and method of the present invention operate in baths at temperatures above 70° C., other temperatures and apparatus are considered within the scope of this invention. For example, when the stripping compositions of the present invention are used in a spray tool apparatus maintained at a temperature or about 80° C., the time required for the stripping solution to completely remove negative tone acrylic photoresists, that are of moderate cure (i.e. 150° C.), the time would be of the order of approximately one-third that of the stripping time required at 70° C. temperature in a static bath. In another embodiment, ultrasonic energy is applied to produce removal rates that are dramatically improved by factors of 3 or 4 at specific temperatures. And in yet another embodiment of the present invention, the stripping composition may operate at a temperature greater than 120° C. to remove the LCP and polyimide polymer substances resulting in the organic matter to be fully dissolved in 10-20 min

[0032] Examples of the kind of polyimide and LCP which may be stripped by the composition of the present invention are shown in Table II below: TABLE II POLYMER TRADEMARKS SOURCE Polyimide Kapton E.I. DuPont de Nemours Polyimide PI - Series & HD - Series HD Microsystems L.L.C. (Hitachi - DuPont) LCP Vectra & Vectron Ticona LCP Zenite E.I. DuPont de Nemours

[0033] The compositions of the kind contemplated by the invention and the method of making is illustrated by the examples which follow. It is understood, however, that the invention is not meant to be limited to the details described therein. In the examples, the percentages provided are percent (%) by weight unless otherwise stated.

General Procedure

[0034] In preparing the stripping compositions of the invention, a preferred order of addition is employed. As stated earlier in this document, the invention includes BTMAH which has been shown to be incompatible with certain organic materials at certain concentrations and conditions. Therefore, it is important to maintain a diluted state when the BTMAH is added to the other components and that the stabilizer, PF, be added as early as possible, and preferably is present in the original BTMAH mixture concentrate. With dilution in mind for the BTMAH stability, it is generally planned to add the BTMAH ingredient last. Therefore, all of the solvents and additives are measured in the desired proportion and introduced into a suitable mixing vessel and thoroughly mixed by stirring. Suitable alternative means may be used to effectively intermix the components such as by concurrent introduction of streams of the respective components, or other suitable known means that fully intersperse the components. Once all of the solvents and additives are mixed, the BTMAH may be added and stirred by the method deemed most feasible. Once the stripping composition is completely mixed, it is deemed stable, with no detectable separation of components and has excellent shelf life when stored at standard warehouse conditions. In the example stripping composition of a kind contemplated by the invention, and comprising 4-8 weight percent BTMAH with PF stabilizer, 60-75 weight percent NMP, 20-30 weight percent EG, surfactant and corrosion inhibitor was employed.

[0035] The photoresist compositions comprise commercially available organic photosensitizer alkaline soluble resin formulations which include (a) a suitable sensitizer such as diazo ketone compounds, e.g., naphthaquione-1,2-diazo sulfonic acid esters, (b) a novolak resin and (c) a suitable solvent such as xylene. Photoresists of this kind are generally described, for example, on page 67 in the work done by D. J. Elliot in Integrated Fabrication Technology, McGraw-Hill Book Company, 1982.

[0036] Equipment and Materials: Equipment, common ware, and materials that are available in an industrial chemistry laboratory were used to screen test a variety of specimens. These included a range of substrate coupons, UV and thermal curing items, identification scopes with a high resolution system having digital imaging, and various ultrasonic cleaning equipment having frequencies of 40, 80 and 170 kHz. Analytical equipment includes physical property and chemical characterization tools from simple pH meters and flash point testers to UV/VIS scanning, GC, and ICP-MS. Where necessary, product purification was used to include distillation (vacuum, up to 10 plates), filtration, and desiccation.

[0037] Procedure: Negative-tone acrylic photoresist (THB-130N, JSR Micro, Inc.) was applied to silicon substrates and treated to the following conditions: a) soft baked at 90-100° C. for 2 hrs, b) selected coupons from (a) are exposed to UV (360 nm) @ 2 W intensity for 5 min, and c) selected coupons from (b) are then post baked at 200° C. for 20 min. The noted coupons are labeled as (a), (b), and (c), with those in the (c) category to be the most rigorous, e.g. full cured. All stripping processes were carried out in small glass vessels, held at 70-80° C., and utilizing static conditions (i.e. no agitation). Observations were done with the aid of an optical microscope (50-400×). In a separate experiment, full cured resist (i.e. JSR THB-130N) is collected in its solid form, e.g. scraped from a polyester substrate, and entered into bath life studies where the presence of an active species is measured vs resist loading.

[0038] Results: Complete removal of the negative type resist was demonstrated using the BTMAH product of the invention vs other stripper blends. Performance was shown to be dependent upon temperature and time. However, for a temperature of 70-80° C., results for scenarios (a), (b), and (c) were deemed to be <5 min, approximately 7 min, and <30min, respectively. No other stripper blend was found to perform as well as the noted invention.

[0039] Bath life (stability) was determined on the invention stripper vs the negative tone acrylic resist (JSR THB-130N). The BTMAH invention was noted to have excess of active species present even as the loading capacity exceeded 5% by weight of the resist solid. The bath life was determined for a concentration range between 0.5-5%, where the 5% value was deemed to be still active. The value of 5% is well beyond the normal processing limit of photoresist stripping.

[0040] Although the invention has been described in terms of specific tests and embodiments, one skilled in the art can substitute other tests and embodiments and these are meant to be included herein. The invention is only to be limited by the scope of the appended claims. 

What is claimed is:
 1. A stripping composition for removing polymeric organic substances from an inorganic substrate, the stripping composition comprising about 4 to about 8 weight percent BTMAH, from about 60 to about 75 weight percent NMP and from about 20 to about 30 weight percent of a glycol, and an effective amount of a stabilizer additive.
 2. The composition of claim 1 wherein the glycol is ethylene glycol.
 3. The composition of claim 1 wherein the stabilizer is paraformaldelhyde.
 4. The composition of claim 2 wherein the stabilizer is paraformaldelhyde.
 5. The composition of claim 1 in which the stripper composition contains up to about 5 weight percent of a corrosion inhibitor.
 6. The composition of claim 1 wherein the stripping composition incorporates up to about 5 weight percent of a corrosion inhibitor and a non-ionic surfactant in amounts not to exceed about 2 weight percent.
 7. The composition of claim 4 wherein the stripping composition incorporates up to about 5 weight percent of a corrosion inhibitor and a non-ionic surfactant in an amount not to exceed 2 weight percent.
 8. The composition of claim 3 in which the BTMAH is about 4 to about 8 weight percent, of the NMP is from about 60 to 75 weight percent and the ethylene glycol comprises about 20 to 30 weight percent.
 9. The composition of claim 8 wherein the triazole corrosion inhibitor is from about 1 to 4 weight percent and the nonionic surfactant is about 0.1 to 1.4 weight percent.
 10. In a method for removing relatively thick film layers of a cured polymeric organic substance from an inorganic substrate the improvement characterized in that a stripping composition comprising about 4 to about 8 weight percent BTMAH, from about 60 to about 75 weight percent NMP and from about 20 to about 30 weight percent of a glycol, and an effective amount of a stabilzer additive is applied to a cured polymeric organic layer to be removed from inorganic substrate, maintaining the stripping composition in contact with said cured polymeric layer for a period of time sufficient to disengage said polymeric layer, and flushing said disengaged layer from the inorganic substrate.
 11. The method of claim 10 wherein the stripping composition glycol is ethylene glycol.
 12. The method of claim 10 wherein the stripping composition contains a paraformaldehyde stabilizer.
 13. The method of claim 10 in which the stripper composition contains up to about 5 weight percent of a corrosion inhibitor.
 14. The method of claim 10 wherein the stripping composition incorporates up to about 5 weight percent of a corrosion inhibitor and a non-ionic surfactant in amounts not to exceed about 2 weight percent. 